In general, in a system in which a plurality of master processors are commonly coupled to one serial bus for communicating between the masters, one master processor at a time is granted authority to transmit data over the bus. By way of example, an integrated system on a single chip, such as a microcontroller, typically comprises several types of functional blocks. To minimize the size of the chip, such system architecture generally comprises a common data bus.
A system, such as a microcontroller, generally has an arbiter for performing an arbitrating operation to control access to the common bus by the integrated functional blocks (or masters). In such systems, to perform arbitration, a bus master that uses a common data bus can be classified with an importance level (or priority level) based on the rate at which the master uses the common bus, wherein a fixed preference arbitrating method is typically used to perform arbitration based on such priorities.
FIG. 1 is a diagram of a conventional system for arbitrating between a plurality of masters for access to common bus. The system includes a common bus 10 and first through nth masters (20-1˜20-N) that are connected to the common bus 10. The masters communicate with each other over the common bus 10. Each of the masters (20-1˜20-N) individually generate first through nth bus request signals (Request_1˜Request_N), respectively, and output the bus request signals to an arbiter 30. The arbiter 30 receives bus request signals (Request_1˜Request_N) from the masters (20-1˜20-N), and then outputs bus grant signals (Grant_1˜Grant_N) to the first through nth masters (20-1˜20-N), respectively, according to a designated preferential order (predetermined priority). The master that receives a bus grant signal is authorized to access the common bus 10 and communicates with other masters.
There are various disadvantages to the system architecture of FIG. 1. For instance, data can be lost and the bus use efficiency can decrease when a master having a lower preferential order has difficulty in receiving timely authority to use the bus. These problems are enhanced as the amount of masters using the bus increases.